1. Field of the Invention
The present invention relates to decurling apparatus for paper web machinery and more particularly to double bar automatic decurling apparatus.
2. Description of the Prior Art
Paper coming from the paper machine in a roll can have various types or curl. This curl, through any subsequent machine which sheets paper, can cause jams or other disruptions.
Core curl is one of the most common types of curl. This occurs as the paper is loosing moisture within the roll and is wrapped around a small diameter core. The paper assumes the shape of the core and the layers of paper around the core. Consequently, the amount of in-the-machine direction curl would increase as the paper unwinds and gets closer to the core. This variable curl is very hard to anticipate and in the case of heavy weight paper, the diameter of the unwinding roll changes so fast that an operator is hard pressed to be able to adjust the decurler bar the correct amount and at the right time. Other types of curl, for example, cross-machine direction, cannot be easily adjusted for without creating other curl within the sheet.
Two types of decurlers are presently used in a sheeting operation, a sharp edged bar type and a roller bar type. The roller type is used where sliding abrasion cannot be tolerated. The sharp edge bar acts not unlike drawing a pice of paper across the edge of a table to produce curl. However, in the case of a sheeting operation, one is trying to overcome existing curl by attempting to curl the sheet in the oposite direction. Since the amount of curl varies as the roll unwinds, remote operator adjustments are necessary during the life of the roll which requires constant monitoring by the operator.